1. Field of the Invention
The present invention relates to masses based on polysiloxanes and containing isoparaffin for use as molding and/or lining compounds, in particular in dentistry. These compounds are silicone pastes cross-linked by condensation or addition reactions for producing exact impressions of dentate, partially dentate or non-dentate jaws and plaster casts in dentistry.
2. Background Information
Silicone pastes are widely used as molding compounds in dentistry. They generally consist of a silicone oil based on a polydimethyl siloxane containing hydroxyl end groups and mixed with fillers and a liquid or pasty curing component containing a metal salt of a monocarboxylic acid as a catalyst and a silicic acid ester as a cross-linking agent. The mixture of silicone oil and fillers may be varied in consistency according to the method of application to be employed. (See, e.g., W. Noll, Chemie und Technologie der Silicone, Verlag Chemie, Weinheim, 2nd Edition, 1964, pages 339-340).
The two components are mixed together before use and cross-link within 2-5 minutes at room temperature due to a polycondensation reaction. This reaction gives rise to small quantities of alcohol in addition to the cross-linked silicone rubber, and the alcohol formed slowly diffuses out of the rubber to produce linear shrinkage which causes inaccuracies in the molding.
The linear shrinkage is much less in the vinyl silicone molding compounds which have only been known in the last few years. These masses consist of two pastes, a basic paste containing silicone oil, filler and cross-linking agent and a catalyst paste containing silicone oil, filler and catalyst.
The silicone oil used in these vinyl silicone compositions is a polydimethyl siloxane containing vinyl end groups, the cross-linking agent contains the reactive SiH groups and the catalyst preferably consists of a platinum complex. In addition to the greater dimensional accuracy of the molding obtained with this system is the advantage that the basic paste and catalyst paste can be more accurately dosed since the pastes have the same viscosity and are mixed in proportions of 1:1. In addition, the pastes are completely flavourless and odourless (see e.g. R.C. Craig, Restorative Dental Materials, The C.V. Moosbe Comp., St. Louis, 1980 page 195 et seq).